Restore evicted owners from plans

- A demanded owner missing from the owner cache is restored from its planned tile (resident or prepared-plan store) instead of drafted again
- Same restore path as persisted tiles; plans identical

core/src/main/java/art/arcane/iris/generation/hydrology/HydrologyPlanner.java

@@ -28,6 +28,7 @@ import java.util.concurrent.CompletableFuture;
 import java.util.concurrent.CompletionException;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ForkJoinWorkerThread;
+import java.util.function.Function;
 import java.util.function.Predicate;
 
 public final class HydrologyPlanner {
@@ -66,6 +67,7 @@ public final class HydrologyPlanner {
     final HydrologyFeatureSitePlanner featureSites;
     final HydrologyRegionalPlanner regional;
     private volatile Predicate<HydrologyTileKey> earlyOwnerScope;
+    private volatile Function<HydrologyTileKey, HydrologyTile> plannedTiles;
 
     public HydrologyPlanner(long worldSeed, HydrologyPlannerSettings settings, HydrologyTerrainSampler sampler) {
         this(
@@ -255,6 +257,14 @@ public final class HydrologyPlanner {
         earlyOwnerScope = scope;
     }
 
+    /**
+     * Where the plans of tiles already planned are found. An owner draft that left the owner cache is
+     * restored from its tile's plan when a neighbour demands it again, instead of being drafted twice.
+     */
+    void usePlannedTiles(Function<HydrologyTileKey, HydrologyTile> source) {
+        plannedTiles = source;
+    }
+
     void clearOwnerDrafts() {
         resolvedOwners.invalidateAll();
         regional.clear();
@@ -300,6 +310,9 @@ public final class HydrologyPlanner {
             return local;
         }
         CrossTileResolvedOwner cached = resolvedOwners.getIfPresent(key);
+        if (cached == null) {
+            cached = plannedOwner(key);
+        }
         if (cached != null) {
             context.remember(key, cached);
             return cached;
@@ -346,6 +359,17 @@ public final class HydrologyPlanner {
         }
     }
 
+    private CrossTileResolvedOwner plannedOwner(HydrologyTileKey key) {
+        Function<HydrologyTileKey, HydrologyTile> source = plannedTiles;
+        HydrologyTile tile = source == null ? null : source.apply(key);
+        if (tile == null || tile.resolvedOwner() == null) {
+            return null;
+        }
+        reuseResolvedTile(tile);
+        CrossTileResolvedOwner restored = resolvedOwners.getIfPresent(key);
+        return restored == null ? tile.resolvedOwner() : restored;
+    }
+
     List<CrossTileResolvedOwner> resolveLowerRankOwners(
             List<HydrologyTileKey> candidateKeys,
             CrossTileResolutionContext context,

core/src/main/java/art/arcane/iris/generation/hydrology/HydrologyTileCache.java

@@ -161,6 +161,17 @@ public final class HydrologyTileCache implements AutoCloseable {
         this.closed = new AtomicBoolean();
         this.localChunks = ThreadLocal.withInitial(LocalChunks::new);
         this.neighbourPrefetchEnabled = true;
+        planner.usePlannedTiles(this::plannedTile);
+    }
+
+    /** A tile already planned, resident or in the prepared-plan store, loaded without planning it. */
+    private HydrologyTile plannedTile(HydrologyTileKey key) {
+        HydrologyTile resident = tiles.getIfPresent(key);
+        if (resident != null) {
+            return resident;
+        }
+        PreparedHydrologyTileStore store = persistentStore;
+        return store == null ? null : store.load(key).orElse(null);
     }
 
     /**